聚乳酸/磁性金属有机框架材料复合熔喷布的制备及其空气过滤性能

Preparation of polylactic acid/magnetic metal organic frame materialcomposite melt-blown fabrics and air filtration performance

为制备一种磁性生物可降解空气过滤用熔喷布,将用水热法合成的磁性金属有机框架材料(MMOF)与聚乳酸(PLA)熔融共混后,再通过熔喷加工工艺制成不同质量比的PLA/MMOF复合熔喷布,对其形貌、结构和性能进行研究。结果表明:随着MMOF质量占比的增加,复合熔喷布中纤维的表面粗糙程度增加,平均直径和孔径也不断增大;当MMOF的含量较高时,复合熔喷布的玻璃化转变温度有所增加,其结晶温度和熔融温度随着MMOF质量占比的增加而升高,加入适量的MMOF对PLA的结晶有异相成核作用,且赋予了PLA/MMOF复合熔喷布磁性;与纯PLA熔喷布相比,PLA/MMOF复合熔喷布的透气率提高,过滤阻力降低,当PLA与MMOF的质量比为1∶0.03时,复合熔喷布的空气过滤效率和断裂强度均达到最大,分别为65.03%和0.21 MPa。

Objective The rapid development of modern industry and agriculture has promoted the progress of society and improved the quality of people′s life.However,the air pollution problem accompanied by the development also poses a serious threat to public health.Melt-blown filter materials with the advantages of high protection,simple preparation process and low price can provide strong defense for human health.In order to prepare the magnetic biodegradable melt-blown air filter material with high filtration efficiency,a magnetic metal organic frame mate\|rial(MMOF)was synthesized and mixed with polylactic acid(PLA)to prepare PLA/MMOF composite melt-blown fabrics.Method MMOF was first synthesized via the hydrothermal method and mixed with PLA resin in different mass ratios by the melt blending in a twin-screw extruder.Then these blends were granulated to obtain PLA/MMOF composite master batches.After that,PLA/MMOF composite master batches were fabricated into the composite melt-blown fabrics with different mass ratios by use of a micro melt-blown testing machine.The morphology,structure,thermal behavior,magnetism,air filtration and mechanical properties of PLA/MMOF composite melt-blown fabrics were characterized and studied.Results It could be seen that the fiber surface of pure PLA melt-blown fabrics was smooth and had a few small grooves.For PLA/MMOF composite melt-blown fabrics,some MMOF particles appeared on the fiber surface.The fiber surface of the composite melt-blown fabrics became more and more rough with the increasing of the mass of MMOF(Fig.1).Moreover,the average fiber diameter and pore size of PLA/MMOF composite melt-blown fabrics also increased when the mass of MMOF increased(Fig.2 and Fig.3).The addition of MMOF did not change the crystalline structure of PLA,but the higher mass of MMOF inhibited the PLA crystallization(Fig.4).When the mass ratio of PLA to MMOF was 1∶0.03 and 1∶0.05,the glass transition temperature of the composite melt-blown fabrics slightly enhanced compared to the pure PLA melt-blown fabric.The crystalline and melting temperatures of the composite melt-blown fabrics increased with the increasing of the mass of MMOF.The moderate input of MMOF had a heterogeneous nucleation effect on PLA crystallization(Fig.5 and Tab.2).When the mass of MMOF increased,the saturation magnetic strength of PLA/MMOF composite melt-blown fabrics was also continuously enhanced(Fig.6).In comparison to the pure PLA melt-blown fabric,the air permeability of the composite melt-blown fabrics was increased,while the filtration resistance reduced.The filtration efficiency of PLA/MMOF composite melt-blown fabric reached the maximum of 65.03%when the mass ratio of PLA to MMOF was 1∶0.03(Fig.7).The tensile strength of pure PLA melt-blown fabric was about 0.16 MPa,and the elongation at break was about 76.80%.When MMOF was incorporated,the tensile strength of the composite melt-blown materials first enhanced and then reduced.The tensile strength reached the maximum of 0.21 MPa when the mass ratio of PLA to MMOF was 1∶0.03.On the other hand,the elongation at break of the composite melt-blown fabrics enhanced with the increasing of MMOF mass(Fig.8 and Tab.3).Conclusion The incorporation of MMOF endows the PLA/MMOF composite melt-blown fabrics with magnetism and improves the air filtration performances.When the mass ratio of PLA to MMOF is 1∶0.03,the filtration efficiency and tensile strength of the composite melt-blown fabric reach the maximum.It is believed that PLA/MMOF composite melt-blown fabric with a mass ratio of PLA to MMOF is 1∶0.03 has the optimal overall performances.The finding of this research provides some theoretical references for the development of magnetic PLA-based melt-blown filter materials.